The present invention relates generally to the measurement of contoured surfaces, and relates more specifically to the measurement of contoured surfaces with phase measurement profilometry (PMP).
The apparel industry is moving toward mass customization in order to be more competitive. This move toward made-to-measure apparel requires underlying technology to facilitate acquiring human body measurements and extracting appropriate critical measurements so that apparel patterns can be selected and altered for the customer. Traditionally, tailors have taken these measurements themselves for their own pattern-altering methods. For this reason, a tailor""s measurements can be very inconsistent when compared with other tailors. An accurate reliable data set of the surface of the body is needed in order to develop consistent body measurements.
Researchers have employed several technologies for body measurement, including two dimensional video silhouette images, laser-based scanning, and white light phase measurement. The white light phase measurement approach has proven to be a promising method of obtaining a full three-dimensional representation of the body without the use and cost of lasers. One example of the use of structured white light, phase measurement profilometry (PMP), is described in U.S. Pat. No. 4,641,972 to Halioua. The structured light and PMP application is well suited for body measurement because of the short acquisition time, accuracy and relatively low cost.
Unfortunately, the approach described in Halioua requires prior knowledge of the image field and continuity of the body surface. As a result, if discontinuities are present in the body surface to be measured, the Halioua method can be inaccurate. Discontinuities can occur if, for example,.the person being measured holds his arms against his sides. In this posture, the forwardmost surfaces of the arms are substantially farther from almost any sensor than those of the chest; yet, when the sensor detects the arms and chest at once, it has trouble differentiating that these objects are positioned at different depths. As a result, the measurement in this and other areas of discontinuity can be quite inaccurate.
One adaptation of the PMP approach is described in co-pending and co-assigned U.S. patent application Ser. No. 08/609,538 to Liang. In this method, after the sensors gather the image data of the body, points of discontinuity are identified by comparing the phase of the structured light at a particular point with the position of that point on a two-dimensional grid. If the point is sufficiently out of phase, it is identified as a point of discontinuity, and the processor that processes the data into three-dimensional information tracks this point as a discontinuity. Unfortunately, data analysis for this approach is heavy and thus can be somewhat slow.
In view of the above, it is an object of the present invention to provide a surface contour measurement system that can quickly and easily measure contoured surfaces such as the human body.
It is another object of the present invention to provide a surface contour measurement system that can detect and properly process discontinuities in the contoured surface.
These and other objects of the present invention are provided by systems, methods and computer program products for measuring, via a computing environment, the surface contour of a three-dimensional object, such as a human body, wherein two-dimensional deformed grating images are converted into three-dimensional data sets. The computing environment includes at least one sensor, computer storage for storing images captured by each sensor, and a data processor for processing images captured by each sensor and generating three-dimensional data sets. Each sensor includes a detector having a lens and an array of pixels for capturing images of the object. Each sensor also includes a projector having a lens and that is configured to project at least one grating pattern onto the surface of the object.
According to one embodiment of the present invention, a grating pattern, having a sinusoidally varying intensity pattern, is projected onto the surface of an object. The grating pattern varies in intensity sinusoidally in a vertical direction and is invariant in a horizontal direction. The grating pattern is referred to as a xe2x80x9ccoarsexe2x80x9d grating pattern.
The projected coarse grating pattern is shifted, preferably four times, by a quarter (or other increment) of a period of the sinusoidally varying intensity pattern. At each shift, a two-dimensional deformed grating image of an area segment of the object surface is captured and stored. Inaccurate data, such as noise and phase measurement errors, are typically removed from the captured two-dimensional deformed grating images. A two-dimensional array of optical phase values is then created, wherein each optical phase value in the array corresponds with a respective pixel in the detector array of pixels.
Optical phase values in the two-dimensional array are then used to generate a plurality of three-dimensional data points that represent respective points on the surface of the object. Each three-dimensional data point corresponds with a respective pixel in the detector array of pixels. Each three-dimensional data point is found by locating, for each pixel in the detector array of pixels, a point on the surface of the object wherein a ray from a respective pixel passing through a nodal point of the detector lens is intersected by a plane of constant phase from the projected first grating pattern passing through a nodal point of the projector lens.
According to another aspect of the present invention, a coarse grating pattern having sinusoidally varying intensity pattern is projected onto an object, and then a xe2x80x9cfinexe2x80x9d grating pattern having a sinusoidally varying intensity pattern is projected onto the object. The fine grating pattern is selected so as to have a period less than that of the coarse grating pattern.
The projected coarse grating pattern is then shifted, preferably four times, and a plurality of two-dimensional deformed grating images are captured and stored as described above. A first two-dimensional array of optical phase values is then created, as described above. Next, the projected fine grating pattern is shifted, preferably four times, and a plurality of two-dimensional deformed grating images are captured and stored as described above. A second two-dimensional array of optical phase values is then created.
Three-dimensional data points that represent respective points on the surface of the object are then located by locating, for each pixel in a detector array of pixels, a point on the surface of the object wherein a first ray from a respective pixel passing through a nodal point of a detector lens is intersected by a first plane of constant phase from the projected coarse grating pattern passing through a nodal point of the projector lens. Then, for each pixel in the detector array of pixels, a point is located on the surface of the object wherein a second ray from a respective pixel passing through a nodal point of the detector lens is intersected by a second plane of constant phase from the projected fine grating pattern passing through a nodal point of the projector lens, wherein the second plane has a phase value within a predetermined range (e.g., between 0 and xcfx80) of phase values that includes a phase value of the first plane.
According to another aspect of the present invention, a scanning chamber for use in determining the surface contour of an object, such as a human body, is provided. A scanning chamber according to the present invention includes a frame having a central compartment and at least one compartment extending outwardly from, and in communication with, the central compartment. The frame is surrounded with a cover of non-reflective material, such as black cloth. An object for which the surface contour is to be determined is positioned within the central compartment. The central compartment preferably has a scanning volume of between about 1.5 cubic meters and about 3.5 cubic meters.
Scanning chambers according to the present invention may have various shapes and configurations. For example, a scanning chamber may have a Y-shaped configuration with three compartments extending outwardly from a central compartment. At least one sensor, and preferably two, is mounted within each outwardly extending compartment. Each sensor includes a detector having a lens and an array of pixels for capturing images of an object surface. Each sensor also includes a projector having a lens and that is configured to project at least one grating pattern onto the surface of the object.